When workflows fail to run properly, it is often difficult to determine the reason for its failure. To help users debug problematic workflows, Taverna can check the validity of data types, input and output ports, and scripts which are involved in services. Taverna also checks whether external Web services, which are invoked from Taverna's WSDL service components, are online. Any issues detected with these workflow components and external tools are signalled in a validation report that can be accessed from its tab in the Workflow Explorer.

Validation report tab

Message type selector

Validation report

Explanation/solution tabs

Text field showing explanation or solution

Ignore message button

Validate report button

The validation report provides a tabular view of all the services found within a workflow. This view is displayed by clicking on the validation report tab (1). This report (2) is generated by checks made against all of the services found within a workflow. Messages are then created for all of these services, the content of which is based on the results of the checks made by Taverna. There are three categories of messages which describe the severity of problems associated with services:

Icon

Severity

OK

Warning

Severe

There is a message for each service in the workflow with an indication of the severity of the problem with it as well as a description. A service that has been checked and judged to be working will have the associated with it. In cases where a service is found to have problems but may still work ok when the workflow is executed, it will be associated with a icon. However, when a processor is marked with a icon, this means that the processor will fail when the workflow is enacted. To deal with validation errors and warnings, see the section on Validation.